1911

Frenchman Henri Pequet makes the first official air mail delivery in Allahabad, British India, moving 6,500 letters to Naini, about 10 kilometers (6.2 mi) away. Carrier pigeons were rendered obsolete and can now be found living homeless in most major cities, seeking employment.

For further reading,

https://en.wikipedia.org/wiki/Henri_Pequet

1930

Astronomer Clyde W. Tombaugh discovers Pluto, once believed to be the ninth planet, at the Lowell Observatory in Flagstaff, Arizona. The existence of an unknown ninth planet was first proposed by Percival Lowell, who theorized that wobbles in the orbits of Uranus and Neptune were caused by the gravitational pull of an unknown planetary body.

For further reading,

https://en.wikipedia.org/wiki/Pluto

1946

Television signals are first successfully transmitted from Washington D.C. to New York City over an AT&T coaxial cable. Now, people could watch people kill each other instead of doing it themselves.

For further reading,

https://en.wikipedia.org/wiki/Television

1967

Robert Oppenheimer, the “father of the atomic bomb,” dies in Princeton, New Jersey, at the age of 62. An expert in quantum theory and nuclear physics, he was enlisted into the fledgling U.S. atomic weapons program in 1941. In 1942, the “Manhattan Project,” as the program became known, was greatly expanded, and Oppenheimer was asked to establish and direct a secret laboratory to carry out the assignment.

For further reading,

http://en.wikipedia.org/wiki/Robert_Oppenheimer